The present invention relates to a vibration absorbing system for absorbing mechanical vibrations, such as reciprocating engine induced mechanical vibration. There are many commercial and industrial environments where engines or other vibration inducing mechanisms are supported at relatively fixed structure with some type of vibration damping system interposed between the support structure and the vibrating mechanism. For example, internal combustion engine driven vehicles are provided with shock absorbing engine mounts which are intended to limit the transmission of engine vibrations into the vehicle body frame and vice versa.
Certain prior art vehicle engine mounts comprise elastically deformable hard rubber cushions or the like for cushioning the transfer of vibrations between the engine and the vehicle frame. Such solid elastically deformable engine mounts do help isolate the vehicle body frame carrying the engine from engine induced mechanical vibrations and the engine from vehicle induced vibrations. However, such engine mounts suffer from disadvantages in that they are unable to attentuate the wide range of mechanical vibrations experienced in use on an automobile. For example, an automobile is designed to operate under many speed, torque, acceleration and deceleration conditions, all of which create different mechanical vibration force, frequency and amplitude patterns. The above-mentioned conventional shock absorber type engine mounts are preset and passive in that they only passively react to vibration forces based on their preset elastic design characteristics. Such vibration isolation mounts can be designed to operate quite well over certain narrow mechanical vibration patterns. However, it is impractical, if not impossible, to design effective preset passive isolation vibration mounts which can attenuate vibrations over all operating ranges of the engine and vehicle.
Certain other prior art vehicle engine mounts utilize a closed fluid shock absorber system for cushioning the transfer of vibrations between the engine and the vehicle frame. Since these fluid shock absorber mounts are closed systems, the same act much like the elastically deformable spring or hard rubber cushion mounts discussed above. Further, in cases of large relative movement between the parts being supported, the shock attenuation substantially diminishes as the fluid pressure rises. Although certain shock absorber mounts provide for multiple fluid chambers and different flow paths depending upon the relative displacement of the parts being supported, such systems are very complex and costly to construct and are also ultimately limited by the total volume of fluid and fluid accommodating space in the overall closed system at an individual shock absorber mount.
The above-mentioned prior art arrangements thus permit an unacceptable level of transfer of vibration forces between the engine and the vehicle frame, and/or involve very complicated, expensive and space wasting constructions.
The internal combustion engine driven automotive vehicle mechanical vibration problems discussed above are but one example of complex mechanical vibration problems that occur. Another example is a drive assembly support for the rotor blades of a helicopter. Such helicopter rotor blade drive assemblies further compound the mechanical vibrations that should be attenuated. Prior attempts to attenuate vibrating force transfers between helicopter blade drive assemblies and the helicopter body or helicopter passenger compartment meet with similar difficulties as described above for the motor vehicles driving on the ground, due again to the wide spectrum of vibration force, frequency and amplitude which are experienced during the helicopter operation. Mechanical vibration isolation problems also occur in stationary engine environments such as driving engines for heating and air conditioning units mounted on commercial buildings or stationary engine electrical generators used at construction sites and at remote areas where electric power must be generated. In these installations, it is desired to minimize mechanical vibration force transfers between the engine and pumps or generators driven by same so as to minimize noise and minimize vibration induced mechanical failures.
An exemplary environment where reduction of mechanical vibration transfer is especially desired involves so-called top floor "penthouse" spaces of large commercial buildings with rooftop heating, venting and air conditioning systems (HVAC systems). Due to vibration induced sound and actual vibration movement of the floors and walls caused by the rooftop HVAC systems, top floors of such buildings are not desirable prime office or living spaces. Again, prior attempts to passively mount the large generators, pumps, etc. for such HVAC systems can only imperfectly and inefficiently respond to the induced mechanical vibration and especially to changes in the vibration spectrum occurring during operations.
The present invention is directed at providing a simple, economical, effective mechanical vibration absorbing system which can respond to a wide range of induced vibration forces, frequencies and amplitudes. The present invention is further directed at overcoming the above-noted problems with prior art arrangements.
These objects are achieved according to the present invention by providing an "active" vibration absorbing system which utilizes a relatively large main fluid pressure accumulator which is actively continuously maintained at a predetermined fluid pressure by a fluid pumping system, and one or more vibration absorber mounts interposed between relatively fixed support structure and the motor or other device inducing the mechanical vibrations, these vibration absorber mounts being continuously acted on by fluid pressure from the main accumulator. The vibration absorber mounts which are constantly in communication with the predetermined pressure of the main accumulator source are effective as responsive vibration absorbers which automatically accommodate for changes in the vibration force, amplitude, and frequency over a wide range.
Due to the relatively small volume of the individual vibration absorber mounts as compared to the main accumulator, restoring pressure fluid supply to the individual mounts is applied in a rapid and reliable manner. In especially preferred embodiments, the hydraulic fluid accommodating volume of the main accumulator is substantially greater than the total volume of all of the individual vibration absorbing mounts connected thereto. In certain preferred embodiments the volume in the main accumulator is more than 10 times the volume of each of the respective vibration absorber mounts connected thereto, including the high pressure connecting lines.
In preferred embodiments of the invention, the main accumulator and pump supplying same are designed so as to provide sufficient fluid pressure and volume response at the individual vibration absorber mounts supplied thereby to handle the predetermined maximum expected vibration induced displacements of the entire system.
In especially preferred embodiments of the invention, the vibration absorber mounts interposed between the relatively fixed support structure and the engine or other vibration inducing mechanism are constructed as individual shock absorbing accumulators having a gas or other spring cushion acting in series with the pressure being supplied via the main accumulator. For example, with a passenger car vehicle engine mounting system, there would be supplied a pump, a main accumulator which is maintained at a constant pressure by the pump, and pressure lines leading from the main accumulator to the individual accumulators at the vibration absorber mounts, preferably distributed symmetrically with respect to the vehicle engine load.
According to certain preferred embodiments, individual vibration absorber support accumulators that are supplied by the main accumulator are constructed as piston and cylinder shock absorber mechanisms which have a fluid pressure space continuously in communication with the main accumulator. In especially preferred embodiments, the fixed and movable parts at the individual vibration support absorber accumulators are constructed as plates which are then in turn mounted to the respective vibration inducing moving part and the relatively fixed part supporting same.
In preferred embodiments of the invention the fluid pressure lines leading from the main accumulator to the individual vibration absorber support accumulators are one-way lines which "deadend" at the individual mounts. Thus, the system is quite simple and economical to construct, while still providing a continuously active support system which adapts to changes in the load "seen" or experienced at the individual mounts over a wide range of vibration displacements.
In especially preferred embodiments for automotive engine mounts, the individual vibration absorber accumulators are constructed to be supported in longitudinal body frame members of the vehicle body. This construction advantageously utilizes existing space on the vehicle body.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.